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61.
Tyan L Sopjani M Dërmaku-Sopjani M Schmid E Yang W Xuan NT Shumilina E Lang F 《American journal of physiology. Cell physiology》2010,299(6):C1379-C1385
Rapamycin, an inhibitor of the serine/threonine kinase mammalian target of rapamycin (mTOR), is a widely used immunosuppressive drug. Rapamycin affects the function of dendritic cells (DCs), antigen-presenting cells participating in the initiation of primary immune responses and the establishment of immunological memory. Voltage-gated K(+) (Kv) channels are expressed in and impact on the function of DCs. The present study explored whether rapamycin influences Kv channels in DCs. To this end, DCs were isolated from murine bone marrow and ion channel activity was determined by whole cell patch clamp. To more directly analyze an effect of mTOR on Kv channel activity, Kv1.3 and Kv1.5 were expressed in Xenopus oocytes with or without the additional expression of mTOR and voltage-gated currents were determined by dual-electrode voltage clamp. As a result, preincubation with rapamycin (0-50 nM) led to a gradual decline of Kv currents in DCs, reaching statistical significance within 6 h and 50 nM of rapamycin. Rapamycin accelerated Kv channel inactivation. Coexpression of mTOR upregulated Kv1.3 and Kv1.5 currents in Xenopus oocytes. Furthermore, mTOR accelerated Kv1.3 channel activation and slowed down Kv1.3 channel inactivation. In conclusion, mTOR stimulates Kv channels, an effect contributing to the immunomodulating properties of rapamycin in DCs. 相似文献
62.
Monique van Scherpenzeel Richard J.B.H.N. van den Berg Wilma E. Donker-Koopman Rob M.J. Liskamp Johannes M.F.G. Aerts Herman S. Overkleeft Roland J. Pieters 《Bioorganic & medicinal chemistry》2010,18(1):267-273
Three different photoprobes were synthesized to label β-glucosidases; one probe was based on glucose, two probes on the iminosugar deoxynojirimycin. The affinity of the probes for three different β-glucosidases was determined. Furthermore, their labeling efficiencies, binding specificities through competition with deoxynojirimycin, and binding specificities in the presence of cell lysate, were evaluated. Especially one showed very high affinity towards non-lysosomal glucoceramidase (IC50 = 20 nM). 相似文献
63.
Differentiation-associated expression of ceramidase isoforms in cultured keratinocytes and epidermis
Houben E Holleran WM Yaginuma T Mao C Obeid LM Rogiers V Takagi Y Elias PM Uchida Y 《Journal of lipid research》2006,47(5):1063-1070
Ceramides (Cers) accumulate within the interstices of the outermost epidermal layers, or stratum corneum (SC), where they represent critical components of the epidermal permeability barrier. Although the SC contains substantial sphingol, indicative of ceramidase (CDase) activity, which CDase isoforms are expressed in epidermis remains unresolved. We hypothesized here that CDase isoforms are expressed within specific epidermal compartments in relation to functions that localize to these layers. Keratinocytes/epidermis express all five known CDase isoforms, of which acidic and alkaline CDase activities increase significantly with differentiation, persisting into the SC. Conversely, neutral and phytoalkaline CDase activities predominate in proliferating keratinocytes. These differentiation-associated changes in isoform activity/protein are attributed to corresponding, differentiation-associated changes in mRNA levels (by quantitative RT-PCR). Although four of the five known CDase isoforms are widely expressed in cutaneous and extracutaneous tissues, alkaline CDase-1 occurs almost exclusively in epidermis. These results demonstrate large, differentiation-associated, and tissue-specific variations in the expression and activities of all five CDase isoforms. Because alkaline CDase-1 and acidic CDase are selectively upregulated in the differentiated epidermal compartment, they could regulate functions that localize to the distal epidermis, such as permeability barrier homeostasis and antimicrobial defense. 相似文献
64.
Sylvia Toet Johannes H. C. Cornelissen Rien Aerts Richard S. P. van Logtestijn Miranda de Beus Rob Stoevelaar 《Plant Ecology》2006,182(1-2):27-40
We studied the effects of elevated CO2 (180–200 ppmv above ambient) on growth and chemistry of three moss species (Sphagnum palustre, S. recurvum and Polytrichum commune) in a lowland peatland in the Netherlands. Thereto, we conducted both a greenhouse experiment with both Sphagnum species and a field experiment with all three species using MiniFACE (Free Air CO2 Enrichment) technology during 3 years. The greenhouse experiment showed that Sphagnum growth was stimulated by elevated CO2 in the short term, but that in the longer term (≥1 year) growth was probably inhibited by low water tables and/or down-regulation
of photosynthesis. In the field experiment, we did not find significant changes in moss abundance in response to elevated
CO2, although CO2 enrichment appeared to reduce S. recurvum abundance. Both Sphagnum species showed stronger responses to spatial variation in hydrology than to increased atmospheric CO2 concentrations. Polytrichum was insensitive to changes in hydrology. Apart from the confounding effects of hydrology, the relative lack of growth response
of the moss species may also have been due to the relatively small increase in assimilated CO2 as achieved by the experimentally added CO2. We calculated that the added CO2 contributed at most 32% to the carbon assimilation of the mosses, while our estimates based on stable C isotope data even
suggest lower contributions for Sphagnum (24–27%). Chemical analyses of the mosses showed only small elevated CO2 effects on living tissue N concentration and C/N ratio of the mosses, but the C/N ratio of Polytrichum was substantially lower than those of the Sphagnum species. Continuing expansion of Polytrichum at the expense of Sphagnum could reduce the C sink function of this lowland Sphagnum peatland, and similar ones elsewhere, as litter decomposition rates would probably be enhanced. Such a reduction in sink
function would be driven mostly by increased atmospheric N deposition, water table regulation for agricultural purposes and
land management to preserve the early successional stage (mowing, tree and shrub removal), since these anthropogenic factors
will probably exert a greater control on competition between Polytrichum and Sphagnum than increased atmospheric CO2 concentrations. 相似文献
65.
Plant Performance in a Warmer World: General Responses of Plants from Cold, Northern Biomes and the Importance of Winter and Spring Events 总被引:10,自引:0,他引:10
During the past three decades the Earth has warmed with a rate unprecedented during the past 1000 years. There is already
ample evidence that this fast climate warming has affected a broad range of organisms, including plants. Plants from high-latitude
and high-altitude sites (‘cold biomes’) are especially sensitive to climate warming. In this paper we (1) review the response
in the phenology of plants, changes in their range and distribution, soil nutrient availability, and the effects on the structure
and dynamics of plant communities for cold, northern biomes; and (2) we show, by using data from an ongoing snow and temperature
manipulation experiment in northern Sweden, that also winter and spring events have a profound influence on plant performance.
Both long-term phenological data sets, experimental warming studies (performed in summer or year-round), natural gradient
studies and satellite images show that key phenological events are responsive to temperature increases and that recent climate
warming does indeed lead to changes in plant phenology. However, data from a warming and snow manipulation study that we are
conducting in northern Sweden show that plants respond differently to the various climatic scenarios that we had imposed on
these species and that especially winter and spring events have a profound impact. This indicates that it is necessary to
include several scenarios of both summer and winter climate change in experimental climate change studies, and that we need
detailed projections of future climate at a regional scale to be able to assess their impacts on natural ecosystems. There
is also ample evidence that the range shift of herbs and shrubs to more northern regions is for the vast majority of species
mainly caused by changes in the climate. This is in line with the observed ‘up-greening’ of northern tundra sites. These rapid
northern shifts in distribution of plants as a result of climate warming may have substantial consequences for the structure
and dynamics of high-latitude ecosystems. An analysis of warming studies at 9 tundra sites shows that heating during at least
3 years increased net N-mineralization from 0.32±0.31 (SE) g N m−2 yr−1 in the controls to 0.53±0.31 (SE) g N m−2 yr−1 in the heated plots (p<0.05), an increase of about 70%. Thus, warming leads to higher N availability in high-latitude northern tundra sites, but
the variability is substantial. Higher nutrient availability affects in turn the species composition of high-latitude sites,
which has important consequences for the carbon and water balance of these systems. 相似文献
66.
Engelborghs S Maertens K Vloeberghs E Aerts T Somers N Mariën P De Deyn PP 《Neurochemistry international》2006,48(4):286-295
To improve clinical, neuropsychological and behavioural characterisation of the cerebrospinal fluid (CSF) biomarkers beta-amyloid((1-42)) protein (Abeta42), protein tau (tau) and tau phosphorylated at threonine 181 (P-tau181) across diagnostic dementia categories, a prospective study was set up. Patients with probable Alzheimer's disease (AD) (n=201), AD with cerebrovascular disease (CVD) (AD+CVD) (n=33), frontotemporal dementia (FTD) (n=27), dementia with Lewy bodies (DLB) (n=22) and healthy controls (n=148) were included. All patients underwent neuropsychological examination and behavioural assessment by means of a battery of behavioural assessment scales. CSF was obtained by lumbar puncture and levels of Abeta42, tau and P-tau181 were determined with commercially available ELISA kits. Negative correlations between CSF Abeta42 levels and aggressiveness (Spearman: r=-0.223; p=0.002) and positive correlations with age at inclusion (r=0.195; p=0.006), age at onset (r=0.205; p=0.003) and MMSE scores (r=0.198; p=0.005) were found in AD. In AD+CVD, CSF Abeta42 levels were correlated with MMSE (r=0.482; p=0.006), Hierarchic Dementia Scale (r=0.503; p=0.017) and Boston Naming Test (r=0.516; p=0.012) scores. In controls, age was positively correlated with CSF tau (r=0.465; p<0.001) and P-tau181 levels (r=0.312; p<0.001). CSF tau and P-tau181 levels correlated significantly in all groups, whereas CSF Abeta42 correlated with tau and P-tau181 levels in healthy controls only. Negative correlations between CSF Abeta42 levels and aggressiveness were found in AD patients. CSF Abeta42 seems to be a stage marker for AD (+/-CVD) given the positive correlations with neuropsychological test results suggesting that CSF Abeta42 might be of help for monitoring disease progression. Different correlations between age and CSF biomarker levels were obtained in healthy controls compared to AD patients, indicating that AD-induced pathophysiological processes change age-dependent regulation of CSF biomarker levels. 相似文献
67.
Nitrogen supply differentially affects litter decomposition rates and nitrogen dynamics of sub-arctic bog species 总被引:5,自引:0,他引:5
High-latitude peatlands are important soil carbon sinks. In these ecosystems, the mineralization of carbon and nitrogen are
constrained by low temperatures and low nutrient concentrations in plant litter and soil organic matter. Global warming is
predicted to increase soil N availability for plants at high-latitude sites. We applied N fertilizer as an experimental analogue
for this increase. In a three-year field experiment we studied N fertilization effects on leaf litter decomposition and N
dynamics of the four dominant plant species (comprising >75% of total aboveground biomass) in a sub-arctic bog in northern
Sweden. The species were Empetrum nigrum (evergreen shrub), Eriophorum vaginatum (graminoid), Betula nana (deciduous shrub) and Rubus chamaemorus (perennial forb). In the controls, litter mass loss rates increased in the order: Empetrum < Eriophorum < Betula < Rubus. Increased N availability had variable, species-specific effects: litter mass loss rates (expressed per unit litter mass)
increased in Empetrum, did not change in Eriophorum and Betula and decreased in Rubus. In the leaf litter from the controls, we measured no or only slight net N mineralization even after three years. In the
N-fertilized treatments we found strong net N immobilization, especially in Eriophorum and Betula. This suggests that, probably owing to substantial chemical and/or microbial immobilization, additional N supply does not
increase the rate of N cycling for at least the first three years. 相似文献
68.
Cornelissen JH Quested HM van Logtestijn RS Pérez-Harguindeguy N Gwynn-Jones D Díaz S Callaghan TV Press MC Aerts R 《Oecologia》2006,147(2):315-326
Plant traits have become popular as predictors of interspecific variation in important ecosystem properties and processes.
Here we introduce foliar pH as a possible new plant trait, and tested whether (1) green leaf pH or leaf litter pH correlates
with biochemical and structural foliar traits that are linked to biogeochemical cycling; (2) there is consistent variation
in green leaf pH or leaf litter pH among plant types as defined by nutrient uptake mode and higher taxonomy; (3) green leaf
pH can predict a significant proportion of variation in leaf digestibility among plant species and types; (4) leaf litter
pH can predict a significant proportion of variation in leaf litter decomposability among plant species and types. We found
some evidence in support of all four hypotheses for a wide range of species in a subarctic flora, although cryptogams (fern
allies and a moss) tended to weaken the patterns by showing relatively poor leaf digestibility or litter decomposability at
a given pH. Among seed plant species, green leaf pH itself explained only up to a third of the interspecific variation in
leaf digestibility and leaf litter up to a quarter of the interspecific variation in leaf litter decomposability. However,
foliar pH substantially improved the power of foliar lignin and/or cellulose concentrations as predictors of these processes
when added to regression models as a second variable. When species were aggregated into plant types as defined by higher taxonomy
and nutrient uptake mode, green-specific leaf area was a more powerful predictor of digestibility or decomposability than
any of the biochemical traits including pH. The usefulness of foliar pH as a new predictive trait, whether or not in combination
with other traits, remains to be tested across more plant species, types and biomes, and also in relation to other plant or
ecosystem traits and processes. 相似文献
69.
70.
Schoonaert K D'Août K Aerts P 《Folia primatologica; international journal of primatology》2006,77(3):246-254
Registering substrate reaction forces from primates during climbing requires the design and construction of customized recording devices. The technical difficulties in constructing a reliable apparatus hinder research on the kinetics of primate locomotion. This is unfortunate since arboreal locomotion, especially vertical climbing, is an important component of the hominoid locomotor repertoire. In this technical paper, we describe a custom-built climbing pole that allows recordings of dynamic 3-dimensional forces during locomotion on horizontal and sloping substrates and during vertical climbing. The pole contains an instrumented section that can readily be modified and enables us to register forces of a single limb or multiple limbs in a broad range of primates. For verification, we constructed a similar set-up (which would not be usable for primates) using a conventional force plate. Data for a human subject walking on both set-ups were compared. The experimental set-up records accurate and reliable substrate reaction forces in three orthogonal directions. Because of its adjustability, this type of modular set-up can be used for a great variety of primate studies. When combining such kinetic measurements together with kinematic information, data of great biomechanical value can be generated. These data will hopefully allow biological anthropologists to answer current questions about primate behaviours on vertical substrates. 相似文献